Oil well casing pipe and method of producing same



Patented Mar. 12, 1935 "UNITED STATES l,993,842 on. WELL CASING PIPEAND'METHOD F PRODUCING SAME Thomas McLean Jasper, Milwaukee, Wis., as-

signor to A. 0. Smith Corporation, Milwaukee, Wis., a corporation of NewYork No Drawing. Application December 10, 1934,

1 Serial No. 756,719%

' 12 Claims.

This invention relates to-oil well casing pi suitable for use. in deepwells.

An object of the invention is to provide a new casing which can be setat a greater depth than 5 the casings which are now generally used.

The trend of the development of the petroleum industry has been in thedirection of increasing the depth of oil wells in order to tap deeplying sources of oil. In the drilling of oil wells the w'ellis linedwith casing to support the walls of the well and to prevent the entranceof water or other undesired substances into the well. The bore of thewell is decreased in steps as the depth is increased and is lined withcasings of decreasing diameter, the casing of smallest diameter beingthe one which extends the farthest distance into the earth.

As oil wells now extend from one to two miles into the earth and as it.is desirable to extend 2o them even farther in order to reach deeperlying deposits of oil, the inner casing which extends the full depth ofthe well is subjected to tremendous external pressures which tend tocause its'collapse, and to large forces acting in the longitudinaldirection of the casing which tend to cause a per- L manent increase inits length or rupture of the casing. The forces acting in the directionof the casing are its weight, and the'pull that is sometimes applied tothe upper end of the casing in order to draw it from the well.

One of the factors which now limits the depth to which oil wells can besunk is the lack of av casing pipe which is not prohibitive in cost andis at the same time of such characteristics as to .35 be suitable foruse in an oil well casing which can be set a great distance in theground. In its more specific aspects, the object of this inventio is toprovide such a casing.

The relatively large diameter surface casings 40 used near the top ofthe well are exposed to relaly'independent of the strength of thematerial of which they are made, or of the yield point of 50 thematerial in compression; atleast sodongas this yield point is above aminimum 'valuefwhich is low when the pipes are of large diameter ascompared to the thickness. Steel of almost any kind has a compressionyield point well above 55 this minimum value, and a large diameter thinpipe of high strength steel with a high yield point in compression willfail by collapsing under external pressure at substantially the samepres-' sure as another pipe which is of the same dimensions but which ismade of a lower strength steel 5 with a lower yield point incompression.

Conditions are differentin a casing pipe in which the diameterisdecreased or the thickness increased, or both, so that the ratio ofdiameter to thickness is smaller than for the larger pipes 10 which havejust been considered. For tubes or pipes with the lower ratios ofdiameter to thickness, the external pressure required to collapse thepipe depends .upon the stress at which the material of the-pipe beginsto yield in comprese 15 sion, in addition to the other factor enumeratedabove. A pipe of this kind made of a. steel with a high yield point incompression will require a much greater external pressure to collapse itthan a pipe of the same dimensions made of a steel with 21 a lower yieldpoint in compression. The smaller diameter casings used in oil wellshave a ratio of diameter to thickness such that the collapsing pressuredepends upon the yield point of the material in compression-to a verylarge extent. -25

This invention provides an oil well casing pipe of this kind which canbe made of plain carbon or alloy steel and mechanically treated to raiseits yield point in compression, and the external pressure which it canwithstand without collaps- 30 mg. Because of the increased pressurewhich this casing can withstand without collapse, it can be set at agreater depth in the ground. Furthermore, the same mechanical treatmentwhich increases the compression yield point of the material used for thepipe and gives the casing pipe increased resistance'to collapse underthe action of an external pressure, also increases the tensile yieldpoint of 'the material in the longitudinal direction of the casing andenables the casing to 40 be subjected to heavier tensile stresses inthis direction without permanent elongation.

The casing pipe of this invention is made of steel and is mechanicallytreated after the pipe is fabricated." In general a plain carbon steelof 0.10 to 0.50 carbon is used but any other suitable steel can beused-if desired. The pipe may be fabricated from the steel in differentways. Electric flash welding or electric arc welding may be used toadvantage but other methods .01? fabrication may be employed; After thepipe has been formed it is compressed radially to a smaller diameter bythe application of force to the outside of the pipe. A suitable methodwhich is also very simple and easy to apply, and which is thereforepreferred, is to place the casing pipe betweentwo semi-cylindrical dies,which, when forced together, form a cylinder of lesser diameter than theexternal diameter of the pipe placed within the dies. The dies are thenforced together, compressing the pipe radially and decreasing itsdiameter. The compression is effected while the casing is cold, that is,at ordinary room temperature. The casing is then ready for use.

The dies may advantageously extend the full length of the casing pipe,but this is not essential since the pipe of this invention can be madeby compressing the pipe in sections by the use of a die which is shorterthan the pipe. The full reduction in diameter can also be made in onestep, or in a series of steps. While any suitable steel canbe used andalloy steels may be preferable for the constructions of casings to reachextreme depth, plane 0.10 to 0.50 carbon steel permits casings to bemade which will reach depths greatly in excess of those attainable withseamless casings now in use, and is consequently often preferable toother steels because of its lower cost.

For annealed 0.10 to 0.50 carbon steel the yield points in compressionand tension are approximately the same, both being equal to about 45,000pounds per square inch for 035-.45 carbon steel and somewhat lower asthe carbon is decreased. By cold compression of easing pipe made fromsuch steel, the yield point in compression in the circumferentialdirection can be raised to well beyond 60,000 pounds per square inch.When casing pipe of 0.35 to 0.45 carbon steel was compressed to producea decrease=in circumference of about 4.75%, it was found that the yieldpoint in compression, as measured in the circumferential direction ofthe casing, was increased to about 80,000 pounds per square inch; whilethe yield point intension, as measured in the longitudinal direction ofthe pipe, was increased to about 60,000 pounds per square inch. Theincrease in tensile yield point is of advantage in that it permits anincreased force to be applied in the longitudinal direction of a stringof easing, as when pulling the casing out of the well, without producinga permanent extension. The increase in compression yield point in thedirection of the circumference of the casing makes the casing capable ofstanding higher external pressures without collapse than if it had notbeen compressed. The difference between the yield point in compressionin a circumferential direction and the yield point in tension in thelongitudinal direction may vary to some extent with the relative flow ofmetal radially and longitudinally in Such compression amounts to no morethan a sizing or trueing of the pipe in dimension. While for valuesabove about 2% reduction-in diameter and of the order of 4.75% or moreconsistent results are obtained and there is a substantially uniformdistribution of the new properties throughout the circumference'andlength of the pipe.

While the compression which is used in making the casing pipe of thisinvention may be varied, it is desirable that the diameter or thecircumference of the casing be decreased by an amount sufficient toproduce a substantial increase in the compression yield point asmeasured in the circumferential direction of the casing. It it furtherdesirable in making the casing of this invention, that the compressionof the casing between dies or otherwise, be such as to produce acompression yield point which is correlated to the diameter and wallthickness of the casing. Thus, when the ratio of the outside diameter ofthe casing to the wall thickness is less than about 30, it isadvantageous to have a compression yield point which is not less than60,000 pounds per square inch, but no corresponding advantage in respectto the external pressure which the casing can withstand without collapseor the depth to which it can be set is obtained with a yield point of60,000 pounds per square inch or higher if the ratio of the diameter towall thickness is greater than 30. The yield points in compression whichcorrespond in a similar way to ratios of diameter to wall thickness ofabout 26 and about 24 are respectively 10,000 and 80,000 pounds persquare inch.

It is characteristic of the casing pipe of this invention that thematerial of the casing preferably possesses difierent physicalproperties in diiferent directions. Instead of possessing a yieldpoint'in compressionwhich is substanially the same as that in tensionand which is substantially the' same in all directions, as would be thecase for annealed or for heat treated steel, the steel in this casingpossesses a high yield point in compression as measured in the directionof the circumference of the pipe, and a yield point in tension measuredin the longitudinal direction, which is likewise higher than the yieldpoint of the annealed steel though lower than the compression yieldpoint as measured in the circumferential direction.

As compared to the annealed steel of which the pipe is made, the steelin the pipe that has been fabricated and subjected to mechanicaltreatment, is of enhanced physical properties, and these enhancedphysical properties are in precisely the directions which increase theutility of the casing pipe for service at great depths. Furthermore, theenhanced properties are roughly in proportion to what are desired formaking a casing pipe of economical proportions, that is, one which is nostronger with respect to one kind of service than with respect toanother. It is found, in general, that for a casing pipe which has ahigh yield point in compression in the circumferential direction, alower yield point in tension in the longitudinal direction of the pipewill suffice to provide an ample factor of safety in this direction topermit the pipe to be used at any setting depth which it can reachwithout danger of failure due to compression by the action ofrexternalpressure.

This casing pipe'possesses important advantages as compared with theseamless casings which are now generally in use in deep wells and whichare made of a relatively high manganese steel which is more costly thanordinary carbon steel. When the casing pipe of this invention is made ofplain carbon steel with the same thickness as the seamless casing madeof the high manganese steel, it can be set at depths which are somethirty per cent greater than can be reached with the seamless casing.The following table shows a comparison between the setting depths for acasing of thisinvention and for Class D seamless casing, the highestclass of seamless casing and the one with which the greatest settingdepths are reached.

The Class D seamless casing for which the figures are given has carbonabout 0.4%, manganese about 1.4%, and silicon about 0.16%, a compressionyield point of about 55,000 pounds per square inch, and elongation in 2inches of over 30.0%, while the casing of this invention with which itis compared has carbon about 0.35-0.45%, manganese about 0.354370%, acompression yield point of about 80,000 pounds per square inch, andelongation in 2 inches of about 30%.

The setting depths for both types of casings are figured on the basis ofan external pressure on the casing of one half pound per square inch foreach foot of depth and a factor of safety'of two. The figures in thethird column for the setting depths of Class D seamless casings aretaken from American Petroleum Institute Supplement No. '1

to A. P. I. Standards No. SA on the care and use of oil country tubulargoods, the supplement being dated January, 1934.

It will be noticed that the new casing when made of carbon steelprovides for setting depths which are, for most of thethicknessestabulated, about thirty per cent greater than for the Class Dseamless casing which is made of a high manganese steel. If the casingof this invention is' made of the same kind of steel as is used for theseamless casing, or of other special alloy steel instead of from plaincarbon steel, a still greater increase in setting depth will beobtained. The

importance of the increased depth which can be reached with thenewcasing is obvious for it means that deep lying oil deposits can nowbe a depth of 7250 feet can be reached with the new casing of plaincarbon steel if the thickness is 0.352 inch, 16% less than the thicknessof the seamless casing. This represents a saving in weight of materialused, and a further-saving in that the new casing'for which the figuresare given, is made of plain carbon steel which is cheaper than the highmanganese jsteel used for the seamless casing.

' inches of about 30%.

It is phenomenal, that considering the great changes effected in thephysical properties of the metal in the making of the casing pipe ofthis invention, there is no appreciable change in either themetallurgical structure as evidenced by microscopic examination, or inthe-density of the metal. It is'also-significant that the ductility ofthe metal, as expressed in percent elongation in 2 inches is notappreciably affected with ordiductility than can be obtained by heattreatment of the same metal under the most favorable conditionsproviding a comparable yield point.

I claim: 1. A well casing of steel. having a ratio of on side diameterto wall thickness not greater than about 30, and-the metal thereofhaving a yield point in compression in a circumferential direction notless than about 60,000 pounds per square inch and a yield point intension in a longitudinal direction less than the yield point incompression in the circumferential direction and substantially greaterthan the yield point in tension of the same metal in completely annealed state.

2. A well casing of steel, the casing having a ratio of outside diameterto wall thickness such that the strength of the casing to resist acollapse is chiefiy dependent upon the yield point of the metal incompression in a circumferential direction, and the metal having a yieldpoint in compression in a. circumferential direction not less than about80,000 pounds per square inch and a yield point in tension in alongitudinal direction less than the yield point in compression in thecircumferential direction and substantially .greater. than theyield'point in tension of the same metal in annealed state.

3. A' well casing of low carbon steel having less than 0.50% carbon, thecasing pipehaving a ratio of outside diameter to wall thickness notgreater than about 30, and the metalthereof being cold compressedsubstantially beyond its natural yield point when in completely annealedcondition to raise the yield point in compression in a circumferentialdirection, and having a yield point in compression in thecircumferential direction in excess of 60,000 pounds'per square inch anda yield point in tension in-a longitudinal direction less than the yieldpoint in compression in the circumferential direction but substantiallygreater than the yield point in tension of the same metal in completelyannealed state, said yield point in compression and said yield point intension being substantially higher than the corresponding yield pointsfor the metal of the casing prior to being cold compressed.

4. A well casingof steel having less than 0.50% carbon, the casing pipehaving a ratio of outside diameter to wall thickness not greater thanabout 24', and the metal thereof being cold com- This shows a muchgreater A 20 pressed substantially beyond its natural yield Y excess of80,000 pounds per square inch and a corresponding yield points for themetal of the casing priorto being cold compressed.

5. A cylindrical low carbon steel casing for lining wells at depths ofthe order of one mileand greater, .the casing being of a size that theratio of its outside diameter to its wall thickness is less than about30, the casing being cold compressed radially to effect a substantialincrease in the yield point of its metal in compression in acircumferential direction, which increase is substantially uniformlydistributed throughout the casing, the yield point in compression of themetal of the casing in a circumferential direction being in excess of60,000 pounds per square inch, and the micro-structure and density ofthe steel of thecasing being substantially the same as that of the samesteel prior to compression of the casing.

6. A cylindrical low carbon steel casing for lining wells at depths ofthe order of one mile and greater, the casing being of a size that theratio of its outside diameter to its wall thickness is less than about26, the casingbeing cold compressed radially to effect a substantialincrease in theyield point of its metal in compression in acircumferential direction, which increase is' substantially uniformlydistributed throughout the casing, the yield point in compression of themetal of the casing in a circumferential direction being in excess of10,000 pounds per square inch, and the micro-structure and density ofthe steel of the casing being substantially the same as that of the samesteel prior to compression of the casing.

7. A cylindrical low carbon steel casing for lining wells at depths ofthe order of one mile and greater, the casing being of a size that theratio of its outside diameter to its wall thickness is less than about24, the casing being cold compressed radially to effect a substantialincrease in the yield point of its metal in compression in acircumferential direction, which increase is substantially uniformlydistributed throughout the casing, the yield point in compression of themetal of the casing in a circumferential direction being in excess of80,000 pounds per square inch, and the micro-structure and density ofthe steel of the casing being substantially the same as that of the samesteel prior to compression of the casing.

8. In a deep well, a steel casing pipe lining the walls thereof andpositioned therein to resist the compression forces of the earthtending-to collapse the casing, said casing having a ratio of outsidediameter to wall thickness such that the strength of the casing toresist collapse is chiefly.

dependent upon the yield point of the metal in compression in acircumferential directionythe casing being cold compressed radially toeflect a substantial increase in the yield point of its metal incompression in a circumferential directlon, the said increase in yieldpoint being sub stantially equally distributed throughout the casing,the metal of the casing having a yield point in compression in acircumferential direction in excess of 60,000 pounds per square inch,and the micro-structure and density of the steel of the.

casing being substantially the same as. that of the same steel prior tocompression of the casing.

9. In a deep well, a steel casing pipe lining the walls thereof andpositioned therein to resist the compression forces of the earthtending. to

collapse the casing, said casing having a ratio of outside diameter towall thickness such that the strength of the casing to resist collapseis chiefly dependent upon the yield point of the metal in compression ina circumferential direction, themetal thereof being treated tosubstantially raise its yield point in compression in a circumferentialdirection and having a substantially greater yield point in compressionin a circumferential v direction than the yield-point in tension in thelongitudinal direction.

10. In a deep well, a steel casing pipe lining the walls thereof andpositioned therein to resist the compression forces of the earth tendingto collapse the casing, said casing having a ratio of outside diameterto wall thickness such that the strength of the casing to resistcollapse is chiefly dependent upon the yield point of the metal incompression in a circumferential direction, the metal of which has ayield point in compression in a circumferential direction in excess of80,000 pounds per square inch and a ductility, as measured by thepercent elongation in 2 inches in standard pulled tension test specimensof .not less than 30% elongation.

11. A well casing of steel having less than 50% carbon, the metal ofwhich has a yield point in compression in a circumferential direction inexcess of 75,000 poundsper square inch and a ductility, as measured bythe percent elongation in 2 inches in standard pulled tension testspecimens,

such increase in yield point throughout the pipe.

'r. MCLEAN JASPER.

